Precoated filters are especially needed in beer brewing to filter out the turbid matter contained in the beer and/or to stabilize the beer. In a known precoated filter, filter candles are used, in which the filter body comprises a wound wire, with gaps between the wire windings serving as fluid passages. The wound wire is either self-supported, or it is held by a carrier communicating with the wound wire. The filter candles of the precoated filter are arranged in an unfiltrate chamber, then passing the filtrate onwards into a filtrate area. For filtration, filtering aids, such as kieselguhr (diatomaceous earth), cellulose, pearlite, activated carbon, plastic fibers, glass fibers, cellulose fibers, or the like, are added to the beer to be filtered. During filtration the filtering aids are precoated on the exterior of the filter body at the beginning of the filtering operation, resulting in the formation of a precoat layer which, in turn, serves as a filtering layer.
The adhesion of the precoat layer to the filter body surface is of great importance, especially to process reliability, because a slipping off may lead to a destruction of the filter cake structure and thus also to an inadequate filter quality. The known filter bodies of wound wire, however, do not always yield an optimum adhesion of the filtering aid to the filter body, so that there may be malfunctions.